An ensemble of thirty physico-chemical characteristics was used to assess the quality of well waters in four urban centers in southern Nigeria: Lagos, Benin City, Warri, and Ekpoma. The characteristics investigated include pH; color; turbidity; salinity; electrical conductivity, EC; total dissolved solids, TDS; total suspended solids, TSS; dissolved oxygen, DO; total hydrocarbon, THC; biochemical oxygen demand, BOD; chemical oxygen demand, COD; and nitrate, nitrite, ammonia, sulfate, and phosphate concentrations. Also monitored were the concentrations of sodium, calcium, potassium, magnesium, chloride, bicarbonate, iron, lead, copper, manganese, zinc, chromium, nickel, and cadmium. The results obtained were compared with World Health Organization, WHO, and Nigerian Federal Ministry of Environment, FME, drinking water standards. The results show that with the well water obtained from Lagos, turbidity, 11.80 NTU; pH, 5.68; EC, 1065.55 lS/cm; TDS, 539.00 mg/L; concentrations of iron, 1.83 mg/L; manganese, 0.14 mg/L; and lead, 1.35 mg/L did not meet the WHO standards. In Warri, pH, 5.19; concentrations of lead, 1.35 mg/L; and chromium, 0.10 mg/L in the well water were above the WHO desirable limits. The results also indicated that the well water from Benin City contained concentrations of chromium, 0.18 mg/L; and lead, 0.20 mg/L that exceeded the recommended WHO limits. In Ekpoma, the pH, 6.00; concentrations of chromium, 0.15 mg/L; and lead, 0.44 mg/L were higher than the desirable limits of WHO. Generally, the assessments revealed that the waters were good and fit for drinking and other domestic application without serious threat to public health.